1. Field of the Invention
This invention is concerned with epoxy based resins water-solubilizable with ammonia or an amine and with water based coating compositions containing them.
2. Description of the Prior Art
It has been proposed to form water dilutable emulsions or dispersions containing epoxy resins for use as water based coatings. Such coatings have disadvantages, and it is highly desirable to provide water-soluble epoxy based coatings. Prior epoxy based coatings have poor shelf life due to the presence of oxirane groups and/or unreacted anhydride.
It is a discovery of this invention that such water based coatings can be obtained by defunctionalization of the oxirane groups by adduction with a bisphenol and making the adducts water-solubilizable by reaction with an anhydride. It has also been found that the anhydride value must be low to obtain increased shelf life.
Insofar as is now known a resin system of this type and coatings containing them have not been proposed.